1. Field of the Invention
The present invention relates generally to a semiconductor structure and process thereof, and more specifically to a semiconductor structure integrating isolation structures and fin structures and process thereof.
2. Description of the Prior Art
With increasing miniaturization of semiconductor devices, various multi-gate MOSFET devices have been developed. The multi-gate MOSFET is advantageous for the following reasons. First, manufacturing processes of multi-gate MOSFET devices can be integrated into traditional logic device processes, and thus are more compatible. Moreover, since the three-dimensional structure of the multi-gate MOSFET increases the overlapping area between the gate and the substrate, the channel region is controlled more effectively. This therefore reduces drain-induced barrier lowering (DIBL) effect and short channel effect. Moreover, the channel region is longer for the same gate length. Therefore, the current between the source and the drain is increased.
On the other hand, due to integrated circuit devices evolving to be smaller and smaller and an increase of integration, distances and arrangements between devices within a semiconductor substrate are decreasing and becoming more tight. Therefore, suitable insulating or isolation has to be formed between each device to prevent each device from junction current leakage, and an insulating or isolation region is reduced to enhance integration in a perfect isolation. In various device isolation technologies, localized oxidation isolation (LOCOS) and shallow trench isolation (STI) are the most often used. In particular, STI has advantages of a smaller isolation region and retaining planarization of the semiconductor substrate. The prior art STI structure is formed between two metal oxide semiconductor (MOS) transistors and surrounds an active region in the semiconductor substrate to prevent carriers, such as electrons or electric holes, from drifting between two adjacent devices through the substrate to cause junction current leakage. STI not only isolates each device effectively but is also inexpensive, which suits semiconductor processes with high integration.